The devastating December 2004 Sumatran earthquake and tsunami, the largest modern natural disaster in terms of people and area affected, is just one grim reminder that societies today are facing increasingly diverse and costly natural and human-triggered threats. Many trends are exacerbating the risks. More people are concentrating in coastal areas, where threats of flooding and storms are heightened, and climate change and sea level rise will amplify these risks. Terrorists have attacked the infrastructures of cities. Population movements, along with global trade and transport, heighten the odds of disease pandemics (see the Editorial on p. 989).

Such diverse and, in many cases, unpredictable threats have led to renewed efforts to improve the resiliency of cities and societies overall. This special issue surveys some of these emerging approaches both for preparing for diverse disasters before they happen and for dealing with them afterward.

Two Viewpoints emphasize related aspects of developing social systems that are resilient to unexpected and diverse threats. Allenby and Fink (p. 1034) discuss strengthening infrastructure, cities, and individual businesses; whereas Adger et al. (p. 1036) highlight steps for improving the safety of coastal regions. Both emphasize that there are steps that can be taken now that will increase security and help society even if a disaster does not strike. For example, preserving natural ecosystems such as reefs diversifies coastal economies, which can enhance recovery from disasters.

The insurance industry is being called on to help in disaster recovery and to guide preparedness in developed and developing nations alike. Mills (p. 1040) examines how the industry must adapt to deal with climate change. In turn, Linnerooth-Bayer et al. (p. 1044) survey some initial approaches that are being developed and tested to expand insurance coverage of these risks to poorer nations.

A major difficulty in recovery from disasters is dealing with the lasting effects they have on the mental health of affected populations. A News story by Miller (p. 1030) describes what is perhaps the broadest effort to date to deal with the psychosocial consequences of disasters and the difficulties of applying Western concepts of mental health to different cultures. Finally, several other aspects of dealing with disasters are explored on Science's Next Wave (see http://www.sciencemag.org/sciext/disasters/